1. Field of the Invention
The present invention relates to a radar ranging device and, in particular, to a merging process for detected target data.
2. Description of the Related Art
Radar ranging devices detect the existence of targets in a forward direction by means of signal processing, which is performed by emitting waves in a forward direction and detecting waves reflected from an object in the forward direction.
When a large target such as a truck exists in the forward direction of the radar ranging device, the radar ranging device may detect a plurality of target data from the one truck. In the radar ranging device, if a plurality of targets are detected, it determines that all targets satisfying predetermined conditions are one target, and performs a process whereby the plurality of targets are merged and target data for one target are output. By this means, the data processing load on devices utilizing the output data from the radar ranging device (for example, a vehicle distance control ECU) is reduced.
Also, in the radar ranging device, when targets detected in a current target detection cycle exist within a predetermined limit around the position of a target detected in the previous detection cycle, it determines that there is continuity between the previously detected target and the currently detected target, and processes them as the same target.
In a process for merging a plurality of detected target data in the prior art, due to the merging of the plurality of target data, the detected position of the target after merging is slightly shifted from the position of the target prior to merging. As a result, when determining continuity between the target merged by the previous process and the currently detected target, it is possible to determine continuity with an erroneous target due to the shift in the detected target.
Also, when a plurality of target data that has been determined to be the same target and subjected to the merging process is outside the merging conditions in the current process, it is taken as a completely new target that has only just appeared, and requires processing of different target data. However, when a new target appears, continuity is determined for each new set of target data. In the continuity determination process, if this new target is continuously detected between a plurality of cycles, it is determined that a new target has appeared. As a result, a target that does not meet the merging conditions causes a delay in the output from the radar ranging device in the same manner as when a new target appears.
Further, when merging between targets, merging is not performed for the same target after merging. As a result, when one target is determined to be a plurality of targets because it is outside the merging conditions, even if both positions are detected in close proximity to each other thereafter, they may not be merged. Consequently, a plurality of sets of target data are output for one target.
The present invention has as its object to accurately perform continuity determinations in the target merging process in a radar ranging device.
The present invention also has as its object rapid performance of new target output processing when a target merged by a merging process has diverged from the merged target data.
A further object of the present invention is to allow, in a radar ranging device, an additional merging process when a target is in proximity after merging.
The present invention was created in order achieve the above objects. In the present invention, in a radar ranging device having a target recognition section for performing a merging process, the target recognition section merges target data and handles the target data as one target when there is continuity between detected target data and those detected target data satisfying predetermined conditions, and stores the target data before execution of the merging process and the target data after execution of the merging process in a buffer memory.
According to the present invention, in the target data merging process, the continuity of each target data is determined using the target data prior to merging stored in the buffer memory, then the continuity of each of the merged target data can be determined using the target data after merging stored in the buffer memory. By this means, even if the detected position of targets change due to merging, continuity can be accurately determined.
Also, in the present invention, when target data not merged in the current process has been merged with other target data in the previous process, whether there is continuity between the target data not merged in the current process and the merged target data in the previous process is determined. If it is determined that there is continuity, the data is taken as being the same target that has diverged, and the target data that has not been merged in the current process is immediately output as diverged target data. As a result, when a target of a previous merging process separates, it is immediately output as new target data without delay.
Also, in the present invention, when target data merged in a previous process meet predetermined conditions, the target data after merging are again merged (re-merged). By this means, only one set of merged target data is output for the same target.